This invention related to polyurethane and/or polyurea elastomers. More particularly, this invention relates to polyurethane and/or polyurea elastomers prepared from active hydrogen-containing copolymers of ethylene oxide and butylene oxide.
Polyurethanes and/or polyureas are commonly prepared by reacting a polyisocyanate with a "polyol" and a "chain extender". The polyol is commonly a polyether prepared by reacting an alkylene oxide, epihalohydrin, tetrahydrofuran or similar compound with an initiator to form a hydroxyl-terminated polyether. This polyether may be aminated, if desired, to provide an amine-terminated polyether. The chain extender is a relatively low equivalent weight compound which contains groups which can react with the polyisocyanate.
The most commonly used polyether polyols are polymers of propylene oxide. However, it has been recognized that the use of poly(ethylene oxide)polyols has certain advantages. In particular, a poly(ethylene oxide)polyol can stress crystallize, providing an elastomer having high tensile strength.
Unfortunately, poly(ethylene oxide)polyols have several very significant drawbacks which render them unsuitable for preparing elastomers. Most important is that polymers of ethylene oxide are very hygroscopic. Elastomers prepared from these polyols are therefore very water sensitive and cannot be used in any humid or aqueous environment. In addition, poly(ethylene oxide)polyols usually form elastomers having poor to moderate tear strength.
It has been attempted to obtain some of the benefits of poly(ethylene oxide)polyols by copolymerizing ethylene oxide (EO) with a higher alkylene oxide. The presence of the higher alkylene oxide units in the polyol reduces the water sensitivity, but permits some of the benefits of the EO units to be obtained. Normally, the alkylene oxide copolymerized with EO is propylene oxide (PO).
In U.S. Pat. No. 4,301,110, it is taught to prepare a polyurethane elastomer using as the polyol certain copolymers of EO and butylene oxide (BO). These polyols are prepared by co-reacting a mixture of EO and BO with an initiator compound, and then "capping" the copolymer with additional EO. The use of this polyol is said to provide for improved heat distortion and tear properties. However, these elastomers have very poor tensile properties.
It would be desirable to provide a polyurethane and/or polyurea elastomer prepared from an EO-containing polyol which exhibits excellent tensile and tear properties, and which is less water-sensitive than those prepared from conventional poly(EO)-containing polyols.